1. Field of the Invention
The present invention relates to a detection of spectral components of an optical signal.
2. Discussion of the Background Art
For a selection of parts or components of an optical signal, wavelength selective splitters/couplers are known that split the optical signal into a plurality of spectral components. Such filters might be built of so-called wavelength division multiplex (WDM) couplers, e.g. 4-port WDM couplers, or of multi-coated glass elements.
For measuring optical properties of an optical device under test (DUT), e.g. an optical fiber, it is known to apply a so-called optical time domain reflectometry (OTDR). For that purpose a short optical pulse is coupled into the DUT, which starts to travel along the DUT and which is partly scattered due to tiny inhomogeneities in the DUT, e.g. the inhomogeneities in the silica structure along the optical fiber. Some of the scattered light travels back to the DUT input. The power of this returning light is measured and put into relation with the elapsed time.
It is further known to separate different spectral components of the backscattered light from an optical fiber and to put these components into relation in order to obtain a distributed physical property of the fiber. Such an arrangement for measuring a temperature distribution along an optical fiber is e.g. described in U.S. Pat. No. 5,618,108.